Kinematic and dynamic axial computed tomography of the patello-femoral joint in patients with anterior knee pain.

Thirty-eight knees of 26 patients with anterior knee pain (12 bilateral) were included in the study. There were 22 women and 4 men, and their average age was 29 years. Axial computed tomography (CT) examination of both knees were done at 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees and 60 degrees of flexion with and without muscle contraction. Images were always taken at the mid-patellar level. Patellar tilt angle (PTA), congruence angle (CA) and sulcus angle (SA) were measured at each knee position. Normal values were also obtained from 14 healthy volunteers (28 knees). Thus, the types of patello-femoral incongruence were determined at each knee position: 1, tilt + lateralisation (TL: 12 knees); 2, lateralisation (L: 4 knees); 3, medialisation (M: 5 knees); 4, lateral to medial instability (LM: 1 knee); 5, tilt (T: 1 knee). Fifteen knees were classified as normal. When the groups were analysed separately, in the TL group the T or L component would have been missed in nine cases if the images were taken only at 30 degrees or only in the first 30 degrees of flexion. In the L group two patellae were reduced at 30 degrees. In three knees in the M group, medialisation began at 10 degrees, 20 degrees and 30 degrees. One patella was reduced at 40 degrees. In the LM case, the patella was lateralised at 0 degrees, 10 degrees, 20 degrees and medialised at 30 degrees and 40 degrees. In the T case, the patella was tilted only at 20 degrees, 40 degrees and 60 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)